1. Field of the Invention
The present invention relates to a process and apparatus for the preparation of a synthetic resin plate having at least two different colors. More particularly, it relates to a process and apparatus for the preparation of a synthetic resin plate having different colors, which comprises supplying a plurality of polymerizable liquid materials differing in color from at least two inlets, passing them through at least two groups of flow paths alternately arranged, extruding and injecting the polymerizable liquid materials into a polymerization apparatus, polymerizing the liquid materials, and withdrawing a plate-shaped product. The resulting product has a striped pattern extending from the surface to the interior or a striped pattern in which the boundary area between the adjacent stripe lines of different colors is gradated.
2. Description of the Prior Art
A plate of different colors having a color pattern only on the surface thereof has been known, and plates of this type are prepared according to various processes. For example, there can be mentioned a process in which a plate is formed and a pattern is printed on the plate by using paints differing in color, and a process in which a film having a color pattern printed thereon is bonded to a plate. Furthermore, plates of different colors in which the boundary area of the color pattern is gradated can be prepared according to a process in which paints differing in hue are applied to the surface of a plate by printing, spraying or dyeing or a process in which a film colored by printing, spraying or dyeing is bonded to the surface of a plate. However, these conventional plates of different colors are inferior as to durability and are defective in that the surface color film can be peeled from the surface of the plate by an external force or with the lapse of time. Moreover, when such a plate is subjected to heating or drawing processing, wrinkles are formed because of differences in the stretchability between the surface color film and the core plate, or the color is thinned in the drawn portion and the color difference between the drawn portion and the undrawn portion becomes prominent, resulting in a reduction of the aesthetic effect.
Plates of different colors having a color pattern extending from the surface to the interior are disclosed in U.S. Pat. Nos. 3,488,246, 3,529,325, 3,526,378, 3,570,056, 3,706,825 and 4,232,078. According to the teachings of these U.S. patents, a polymerizable liquid material including a filler and a colorant and having a high viscosity are appropriately mixed together by a three-stage mixing apparatus and the polymerizable liquid material is polymerized and cured to obtain an opaque plate-shaped product having a pattern resembling a marble pattern. The characteristic feature of this preparation process resides in appropriate mixing, and the pattern is changed according to the concentration, viscosity and flow rate of the starting material and the state of the mixer. Therefore, the probability of formation of a predictable pattern on the surface of the plate is low. It is thus difficult to produce an aesthetic color pattern with a good reproducibility.
The technique disclosed in U.S. Pat. No. 4,232,078 is one developed by the inventor of the present invention. According to the technique of this patent, at least two polymerizable liquid materials differing in color are injected into a polymerization apparatus and are polymerized and cured to gradate the boundary area between the two liquids. In a plate of different colors prepared according to this process, the hue is changed only in the direction of the width but the hue is substantially uniform in the direction of the thickness. Accordingly, the formed pattern is relatively monotonous and lacks depth.